Along with development of technology, sizes of materials and components have been reduced to a nanoscale, and people have entered a new nanotechnology era. In various nanotechnology developments, nano microscopy technique and nano manipulation technique have attracted extensive attention, and based on the aforementioned techniques, atoms, molecules or molecule arrangement can be controlled according to material characteristics, and new techniques applied to human life can be further created, for example, an optical lithography technique, a nanomaterial sensing technique, micro drag detection, DNA detection, etc. However, in development of optical technology, since an optical lens is limited by Abbe's diffraction limit, a size of a light source can only be about several hundreds of nanometers or more, which greatly limits the development of the optical technology. On the other hand, in the optical detection technique, since a difference between sizes of a light source and a nano substance is too large, efficiency of an interaction force between light and the nano substance is decreased, which causes inadequate sensitivity of the optical detection, for example, a weak Raman signal. Therefore, under the current nanotechnology development, it is one of the popular research trends to develop a stable nanometer light source.
In the current nanotechnology development, research of surface plasmon occupies an important position. The surface plasmon is a collective electron gas resonance wave existing at the interface between a metal and a dielectric, and such resonance wave may produce an electromagnetic field nanofocus effect to form a nano light source through a specific structure design, wherein the nano light source has a nanoscale, and may produce a high efficiency interaction force with a substance with the nanoscale, so that sensitivity of the optical detection is improved to reach a single molecule level. In a daily life level, the nano light source technology can be applied to detect contaminants in environment and food such as plasticizers, environmental hormones, phosphates, etc., or applied to biomedical field detection, for example, non-dye based biological calibration, antigen detection, DNA synthesis, drug or biological screening and tissue testing, etc. Moreover, in the field of microscope, the nano light source technology can be combined with a tip enhanced Raman spectroscopy (TERS) method for applying to an atomic force microscope (AFM), in this way, such device has both of sensitivity of surface-enhanced Raman spectroscopy (SERS) and an ultra high spectral resolution provided by the AFM.
In current development of nano light source structure, a front end of a needle-like structure of a probe is opened by 100 nm, and the nanoscale light source is produced at a near-field of the opening, though a light intensity of the nanoscale light source of such structure is limited by Bethe's theory, such that a light flux of the nano light source only has a light conversion efficiency of 10−5 to 10−7 to decrease a signal to noise ratio. In order to maintain an enough signal to noise ratio to decrease a measuring time or an lithography exposure time, an actual size of an aperture of such structure is about 50 to 100 nm, which results in a fact that the optical resolution is only 50 to 100 nm and a spatial resolution is greater than 100 nm.